Underwater detection device

ABSTRACT

An underwater detection device for detecting underwater by transmission and reception of an ultrasonic signal is provided. The device includes a transmission module for transmitting the ultrasonic signal underwater, a reception module for receiving an echo signal of the transmitted ultrasonic signal, a bottom detection module for detecting a bottom based on the echo signal from the bottom, a bottom-sediment determination module for calculating probabilities of the bottom sediment on how much the bottom sediment contains each of predetermined bottom sediment types based on the echo signal and a bottom-sediment display module for displaying a texture representing each of the bottom sediment types below the bottom being displayed based on the probabilities.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to Japanese PatentApplication No. 2007-022279, which is filed on Jan. 31, 2007, the entiredisclosure of which is hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to an underwater detection device fordetecting underwater conditions by transmission and reception of anultrasonic signal.

BACKGROUND

As shown in FIG. 1, a conventional underwater detection device 1receives an echo of an ultrasonic wave transmitted underwater from aship bottom, and displays based on the received echo level, etc. Such anunderwater detection device 1 typically includes a calculation module500, a transmission module 100, a transmission/reception switchingmodule 200, a transducer 300, a reception module 400 and a displaymodule 600. Hereinafter, the detection and display method of theunderwater detection device 1 will be explained.

First, the transmission module 100 amplifies a transmission drivesignal. The transmission drive signal is applied to the transducer 300through the transmission/reception switching module 200, and the module200 then transmits the ultrasonic signal. The transmitted ultrasonicsignal is reflected by an object in water, such as a fish or a bottom,and the echo signal is received by the transducer 300. The received echosignal passes through the transmission/reception switching module 200,and then the signal is processed, such as band restriction andamplification by the reception module 400. The processed signal iscalculated by the calculation module 500 so as to be displayed, and apredetermined display is then performed by the display module 600. Thecalculation module 500 typically includes a bottom detection module 51,a bottom-sediment determination module 52, a fish detection module 53,and a fish-length calculation module 54. The display module 600typically includes a bottom-sediment display module 61 and a fish-lengthdisplay module 62.

The bottom detection module 51 and the fish detection module 53calculate positions of fish or bottom based on a time required for thetransducer 300 from the transmission of the ultrasonic signal to thereception of the echo signal from the fish or bottom. Thebottom-sediment determination module 52 determines a bottom sedimenttype based on the echo level from the bottom, etc. The determinationresults for the bottom sediment type includes information, such as theecho level from the bottom itself, the echo level from secondaryreflection, temporal variations of these echo levels, a determinedbottom sediment type, or the like. The fish-length calculation module 54calculates a size of the fish (i.e., fish length) based on the echolevel from the fish.

FIG. 2 is a display example of a fish finder having such a configurationas described above, such as disclosed in Japanese Unexamined PatentPublication No. 2002-90453. As shown in FIG. 2, the bottom-sedimentdisplay module 61 displays predetermined colors associated with thebottom sediment types (from A1 to A4) at the bottom of a display screenbased on the bottom sediment types determined by the bottom-sedimentdetermination module 61.

Further, Japanese Unexamined Patent Publication No. 2004-93429 disclosesa similar display configuration in FIG. 2 thereof, this displayconfiguration displays colors corresponding to first through Nth echosignals from the bottom are displayed using N blocks on a separatedisplay screen from the display screen on which a shoal of fish aredisplayed.

Returning to FIG. 2, the fish-length display module 62 displays a symbolrepresenting a fish in a size corresponding to the fish lengthcalculated by the fish-length calculation module 54. The symbol may becolored based on the echo level and may be textured as similar to thatof the actual fish. Further, the fish-length display module 62 displayscharacters, such as a number indicating the fish length in proximity tothe displayed fish symbol.

Hereinafter, further referring to FIG. 2, a display example displayed bythe display module 600 of the underwater detection device I will beexplained. In FIG. 2, the vertical axis indicates water depth and thehorizontal axis indicates time. Further, because the fish findertransmits ultrasonic signals perpendicularly downward, the displayscreen is updated one vertical line at a time according to eachtransmission and reception, while the display screen is scrolled to theleft. Thus, the latest data is always displayed at the right end of thedisplay screen.

In FIGS. 2, A1 to A4 (i.e., echo images) are displayed by thebottom-sediment display module 61 to display the bottom sediment. Theecho images A1-A4 are represented by colors according to the types ofthe corresponding bottom sediment sections. “B” is a texture displayedby the first fish-length display module 62, and the texture has a sizecorresponding to the fish length. The texture is an imitation of thefish appearance, and typically is provided with several sizes accordingto fish length. Further, “C” is a character or number displayed inproximity to the texture B to indicate the fish length. “D” is an echoimage of a shoal of fish, “E” is a character or number indicating awater depth, “F” is an echo image of a bottom, and “G” is an echo imageof an oscillation line.

However, as mentioned above, the display configuration for the bottomsediment of the conventional underwater detection device onlydistinguishes the bottom-sediment types by color tone, and a user cannotintuitively distinguish the bottom sediment types only by viewing thedisplay screen. That is, in order to determine the bottom sedimenttypes, the correspondence of the colors to the bottom sediment typesmust be understood. Further, Japanese Unexamined Patent Publication No.2004-93429 also discloses a more accurate bottom sediment typedetermination which can be facilitated by displaying the first to Nthecho signals from the bottom in predetermined display areas andpositions. However, this arrangement requires the user's subjectivity orexperiences.

Further, for the display corresponding to the fish, the device solelydisplays the fish texture corresponding to the level of echo signal.Therefore, the determination of fish type requires the user'sexperiences.

SUMMARY

In order to address these problems, the present invention provides anunderwater detection device capable of allowing a user to intuitivelydetermine a bottom sediment type and a fish type, as well as anunderwater condition from a display screen without depending on theuser's experiences. The underwater detection device may be able toexpress the underwater condition with more accuracy by associating waterdepth information and water temperature information with the display ofthe bottom sediment or the fish.

According to one aspect of the invention, an underwater detection devicefor detecting underwater by transmission and reception of an ultrasonicsignal is provided. The device includes a transmission module fortransmitting the ultrasonic signal underwater, a reception module forreceiving an echo signal of the transmitted ultrasonic signal, a bottomdetection module for detecting a bottom based on the echo signal fromthe bottom, a bottom-sediment determination module for calculatingprobabilities of the bottom sediment on how much the bottom sedimentcontains each of predetermined bottom sediment types based on the echosignal, and a bottom-sediment display module for displaying a texturerepresenting each of the bottom sediment types below the bottom beingdisplayed based on the probabilities.

The underwater detection device may further includes atexture-total-count calculation module for calculating a total count ofthe texture to be displayed below the bottom, and abottom-sediment-texture-count calculation module for calculating atexture count for each of the bottom sediment types based on the totalcount of the texture and the probabilities calculated by the bottomsediment determination module. The bottom-sediment display module maydisplay based on the texture count for each of the bottom sediment typescalculated by the bottom-sediment-texture-count calculation module.

The underwater detection device may further include a bottom-sedimentmemory module for storing the probabilities of the past calculated bythe bottom-sediment determination module. Thebottom-sediment-texture-count calculation module may calculate thetexture count for each of the bottom sediment types based on theprobabilities stored in the bottom-sediment memory module.

The underwater detection device may further include a fish detectionmodule for detecting a fish based on the echo signal received by thereception module, a fish-type determination module for determining atype of the fish based on at least one of the echo signals, watertemperature, water quality, water area and depth, and a fish-typedisplay module for displaying a texture representing the fish type basedon the fish type determined by the fish-type determination module.

The underwater detection device may further include a firstwater-depth-variation display module for varying the texturerepresenting the bottom sediment or the fish depending on a water depth.

The underwater detection device may further include a secondwater-depth-variation display module for displaying a background towhich gradation is applied based on a water depth.

According to another aspect of the invention, an underwater detectiondevice for detecting underwater by transmission and reception of anultrasonic signal is provided. The device includes awater-depth-variation display module for displaying a background towhich gradation is applied based on a water depth.

The water-depth-variation display module may apply the gradation only toa predetermined water depth range.

The underwater detection device may further include awater-temperature-variation display module for displaying a backgroundto which a color is applied based on a water temperature. The gradationapplied by the water-depth-variation display module may be a darkness ofthe color of the background.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a configuration of a conventionalunderwater detection device.

FIG. 2 is a view showing a display configuration by the conventionalunderwater detection device shown in FIG. 1.

FIG. 3 is a block diagram showing a configuration of an underwaterdetection device according to Embodiment 1 of the present invention.

FIG. 4 is a view showing another configuration of the underwaterdetection device according to Embodiment 1 of the present invention.

FIGS. 5A-5C are views showing display positions of textures representingbottom sediment.

FIGS. 6A and 6B are views showing a relationship between a water depthand gradation.

FIG. 7 is a block diagram showing a configuration of an underwaterdetection device according to Embodiment 2 of the present invention.

FIG. 8 is a view showing a display configuration of the underwaterdetection device shown in FIG. 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Embodiment 1

Hereinafter, an underwater detection device 2 according to Embodiment 1of the present invention will be explained referring to FIGS. 3, 4,5A-5C, 6A and 6B. First, as shown in FIG. 3, the underwater detectiondevice 2 includes a transmission module 100, a transmission/receptionswitching module 200, a transducer 300, a reception module 400, acalculation module 50, and a display module 60. In this embodiment, thetransmission module 100, transmission/reception switching module 200,transducer 300, and reception module 400 are similar to that of theconventional underwater detection device 1 described above and, thus,explanations thereof will be omitted herein. Hereinafter, specificprocesses of the calculation module 50 and the display module 60 will beexplained.

The calculation module 50 includes a bottom detection module 51, abottom-sediment determination module 52, a fish detection module 53, afish-length calculation module 54, and a fish-type determination module55. In this embodiment, the bottom detection module 51, bottom-sedimentdetermination module 52, fish detection module 53, and fish-lengthcalculation module 54 are similar to that of the conventional underwaterdetection device 1 described above and, thus, explanations thereof willbe omitted herein.

The fish-type determination module 55 determines a fish type based on atleast one of an echo signal from the fish detected by the fish detectionmodule 53, water temperature, water quality, water area, and waterdepth. For example, the module 55 may determine a fish type thatproduces a typical echo signal based on the detected echo signal, andmay determine a fish type that inhabits in water at high or low watertemperature based on the detected water temperature. Further, the module55 may determine a fish type that inhabits in freshwater or saltwaterbased on the detected water quality, and may determine a fish type thatinhabits in a typical area or water depth based on detected the waterarea or water depth. Further, the module 55 may narrow down the fishtype by combining the detections of different detectors. Here, theinformation, such as the water temperature, water quality, water area,or water depth, for the determination of the fish type may be manuallyinputted by the user, or may be automatically acquired from a waterthermometer, a water quality meter, a positioning system, the bottomdetection module 51, etc.

The display module 60 includes a bottom-sediment display module 66, afish-length display module 62, a fish-type display module 63, awater-depth-variation display module 64, a water-temperature-variationdisplay module 65. In this embodiment, the fish-length display module 62is similar to that of the conventional underwater detection device 1and, thus, explanation thereof will be omitted herein.

The bottom-sediment display module 66 displays a texture representing abottom sediment based on the determination result of the bottom-sedimentdetermination module 52, below the displayed bottom in accordance withthe detection by the bottom detection module 51. As shown in Table 1below, the determination result of the bottom-sediment determinationmodule 52 includes probabilities of which a bottom sediment typecorresponds to which bottom sediment among predetermined two or moretypes of the bottom sediments, such as rocks, sands, stones, or mud.

TABLE 1 Parameter Depth Rocks Sands Stones Mud Texture

Data 20 m 70(%) 30(%) 0(%) 0(%)

Table 1 shows an example of the water depth and the correspondingprobabilities of the bottom sediment types (hereinafter, referred to as“bottom sediment data”) where the water depth is 20 m. This data showsthe probabilities in which the bottom sediment contains 70% of rocks,30% of sands, 0% of stones and 0% of mud. The bottom-sediment displaymodule 66 displays a texture of the bottom sediment type with thehighest probability among those determined.

The displayed textures may extend to the bottom of the display screen,and if a texture size is larger than an area into which the texture isdisplayed, the oversized texture portion may be hided without beingdisplayed, while if the texture size is smaller than the area into whichthe texture is displayed, two or more textures may be used. Next, thedisplay method when the texture is smaller than the area will beexplained referring to FIG. 4, and FIGS. 5A-5C that show displayexamples.

As shown in FIG. 4, the bottom-sediment display module 66 includes afirst texture display module 661, a texture determination module 662 andan irregular display module 663. FIGS. 5A-5C show a lower right sectionof the display screen of the underwater detection device 2, and in thesefigures, a square frame is provided around each texture for easier view.This display screen is by a SVGA (i.e., resolution of 800×600 dots), atexture size (one block) is 30×40 dots (vertical×horizontal) anddetection information obtainable from one transmission and reception is800×1 dots (one line in the vertical direction). Further, the detectioninformation is typically updated for every one transmission andreception to scroll the display screen from the right to the left.

First, the first texture display module 661 displays a first texture inthe bottom display area. This bottom corresponding to the first textureis detected by the bottom detection module 51. The water depth may becalculated by multiplying a half of a time necessary for transmission ofan ultrasonic wave and reception of the echo signal from the bottom bythe transducer 300, by a propagation rate of the ultrasonic wave.

The first texture may be updated every 20 transmissions and receptions.Further, as shown in FIG. 5A, an upper portion of the first texturecontacts the bottom surface, and a lateral half portion of the texture(e.g., 20 dots) is displayed on the display screen.

The texture determination module 662 determines a type of the texture tobe displayed. As described above, the texture to be displayed representsthe bottom sediment type with the highest probability among thosecalculated by the bottom-sediment determination module 52. The texturesmay, but not limited to, be stored in the memory corresponding to thebottom sediment types. One texture may correspond to one of the bottomsediment types. Alternatively, two or more similar textures may bestored for one of the bottom sediment types to select one of thetextures.

As shown in FIG. 5B, the textures may be sequentially displayed at leastto the bottom of the display screen by the irregular display module 663.Specifically, the module 663 sequentially displays the textures so as tobe irregularly overlapped for each other by 5-10 dots (approximately, ¼of a texture) in the vertical direction so that an irregular displaypattern is created. Similarly, in the horizontal direction, the texturesmay be displayed so as to overlap for each other within ±5 dots.

Alternatively, if two or more similar textures are provided for a bottomsediment type as described above, these textures may not be overlapped,and instead, the two or more similar textures may be arranged to createan irregular display pattern. Alternatively, the same texture ofdifferent sizes may provide a similar effect.

Thus, as shown in FIG. 5C, each time the detection information isupdated, the textures in the corresponding line shift by one line at atime to the left, and when the display information for 20 dots isupdated in the horizontal direction, the next textures are displayed asshown in FIGS. 5A and 5B. Here, when the next texture overlaps theprevious texture, the next texture may be displayed so as to overlie theprevious texture. As described above, the underwater detection device ofthis embodiment can realistically display the bottom sediment and, thus,the user with a few experiences can also easily know the bottom sedimenttype.

Display order of the textures in the vertical direction may be towardsthe bottom end of the display screen from the bottom (of water), ortowards the bottom (of water) from the bottom end of the display screen.Alternatively, the vertical display area on which the textures are to bedisplayed may be calculated in advance to display all of the texturessimultaneously. The bottom sediment may be more realistically displayedby obscuring the texture boundary. The information acquired by onetransmission and reception is not limited to one line in the verticaldirection on the display screen, and the display updating cycle of thetexture is not limited to 20 transmissions and receptions.

The fish-type display module 63 displays textures representing a fishtype based on the determination of the fish-type determination module55. Specifically, the texture representing the determined fish type maybe displayed so that the center of gravity of an area corresponding tothe echo from the fish (i.e., this location may be the same as where thefish detected by the fish detection module 53 should be displayed) andthe center of gravity of the texture are arranged at the same locationon the display screen. The texture size may, but not limited to befixed. The texture size may vary based on the fish length by thefish-length display module 62. With the above configuration, theunderwater condition can be realistically displayed, while increasingthe amount of information provided and, thus, the fish type can beunderstood even by the user with a few experiences.

The water-depth-variation display module 64 displays a background towhich gradation is applied based on the water depth. Specifically, thegradation may be darker in color for deeper water depth, as shown inFIG. 6B. FIG. 6A shows a relationship between the water depth and thedarkness of the background, and FIG. 6B shows an example of the displayscreen to which the gradation is applied. Therefore, the water depthinformation can be graphically displayed with the underwater conditionthat is described as above. Further, the water depth of 150 m or deeper,or vice versa, may also be displayed in the same darkness in color toclearly distinguish the water depth of 150 m. The relationship betweenthe water depth and the background gradation may be automatically variedbased on the displayed range, or may be manually set by the user.Further, the gradation may not be limited to the darkness in color, butmay be expressed by different colors, brightness, etc.

Further, the color and contour of the texture displayed by thebottom-sediment display module 66 and the fish-type display module 63may be changed based on the water depth by the water-depth-variationdisplay module 64. For example, as the water depth becomes deeper, thechroma or brightness of the texture may be reduced, or the contour maybe graded or fuzzily displayed (e.g., blurred). By configuring asdescribed above, even in a case that the background is a single color toemphasize on the other information, such as the texture, the water depthinformation can be provided by the texture instead of the background toclearly indicate the water depth variation.

The water-temperature-variation display module 65 displays thebackground to which color is applied based on the water temperature. Forexample, blue may be displayed for a low water temperature, and red maybe displayed for a high water temperature. Therefore, the underwatertemperature environment can be expressed and, thus, the user can moreeasily understand the underwater condition. Further, the color displayedby the water-temperature-variation display module 65 may be combined toadd the gradation of the water-depth-variation display module 64 to itto have the both effects. The information on the water temperature maybe directly inputted by the user, or may be automatically acquired froman appropriate device, such as the water thermometer.

Embodiment 2

The underwater detection device 2 according to Embodiment 2 causes abottom-sediment display module 66′ to display the textures in accordancewith the probabilities of the bottom sediment types based on thedetermined bottom sediment types (i.e., bottom sediment data). Forexample, the number of textures proportional to the probability of onebottom sediment type may be calculated and the textures of the numberfor each bottom sediment type are displayed. By this configuration, theuser can easily view the bottom sediment types simply from the displayscreen, and can also understand the probability of each bottom sedimenttype. Hereinafter, a specific operation of the bottom-sediment displaymodule 66′ will be explained. The other configuration of Embodiment 2 issimilar to that of Embodiment 1 and, thus, explanation thereof will beomitted.

As shown in FIG. 7, the bottom-sediment display module 66′ includes atexture-total-count calculation module 664, a bottom-sediment memorymodule 665, a bottom-sediment-texture-count calculation module 666 andan irregular display module 667. The texture-total-count calculationmodule 664 calculates the total count of the textures required for anarea where the bottom sediment information is displayed below the bottomsurface detected by the bottom detection module 51. The total count ofthe textures is calculated by dividing the area where the textures aredisplayed by the texture size to be placed. In this embodiment, the areawhere the bottom sediment information is displayed is an area from thewater depth of the bottom detected by the bottom detection module 51 tothe water depth corresponding to the bottom end of the display screen.

The bottom-sediment memory module 665 stores the information on thebottom sediment determined by the bottom-sediment determination module52. The bottom sediment information includes probabilities of certainbottom sediment on how much the bottom sediment contains each ofpredetermined bottom sediment types. The memory module 665 may store theprobabilities of the bottom sediment types used for the display of theprevious texture (i.e., the probabilities determined 20 transmissionsand receptions earlier), or may store the probabilities obtained foreach transmission and reception.

The bottom-sediment-texture-count calculation module 666 calculates thetexture count necessary for each of the bottom sediment types. Thiscalculation is performed based on the total count of the texturescalculated by the texture-total-count calculation module 664, and theprobabilities of the bottom sediment types calculated by the bottomsediment determination module 52. For example, the calculation may beperformed so that the texture count corresponding to each bottomsediment type is proportional to the probability of the bottom sedimenttype. Alternatively, the calculation module 666 may calculate thetexture count based on an average value of the probabilities of thebottom sediment types calculated by the bottom-sediment determinationmodule 52 and past probabilities of the bottom sediment types stored inthe bottom-sediment memory module 665, or may calculate it based on acorrelation thereof. Thus, by taking the past information on the bottomsediment into consideration, error factors can be reduced to provide theuser with more accurate information.

The irregular display module 667 displays the textures sequentially tothe bottom end of the display screen so that the textures are arrangedin an irregular pattern. The method of irregularly displaying thetextures is similar to that of the irregular display module 663 inEmbodiment 1. However, in this embodiment, the textures to be displayedmay be two or more types. Therefore, by presetting the order orpriorities of the various types of the textures to be displayed, theoverlapping textures may be stably and uniformly displayed on thedisplay screen even when they are updated from the side of the displayscreen (i.e., from the right in this embodiment). For example, apredetermined display order may be set so as to have overlyingpriorities of rocks, sands, stones and mud from the top to the bottom.Next, a calculation method of the total count of the textures calculatedby the texture-total-count calculation module 664 and the count of eachtexture calculated by the bottom-sediment-texture-count calculationmodule 666 will be explained referring to Table 1.

If the display range of the underwater detection device 2 in thisembodiment is 200 m, 720 dots serves as an area showing the bottom among800 dots of the vertical dimension of the display screen. Further, whensequentially displaying the textures so as to be overlapped for eachother by approximately an ¼ of each texture from the bottom (20 m indepth) to the bottom end of the display screen (200 m in depth), an areato be occupied by a texture is 30×¾=22.5 dots in the vertical direction.Therefore, in this case, the required texture count is 720/22.5=32pieces. When the calculated texture count is not an integer value in theabove case, decimal points may be rounded.

Preferably, in this embodiment, a rate of the texture counts of therocks and sands may be approximately 70:30 so that each type of thetextures to be displayed corresponds to the probability of the bottomsediment type as shown in Table 1. That is, after displaying 22 piecesof the rock textures sequentially from the corresponding displayposition, 10 pieces of the sand textures may be displayed. As describedabove, the priority between rocks and sands is rocks and, then, sandsfrom the top. Thus, the irregular display module 667 displays thetextures based on the calculated counts and types, and the priorities,as described later.

Alternatively, each texture count may also be calculated based on thepast bottom sediment data stored in the bottom-sediment memory module665. For example, the texture count corresponding to each bottomsediment type may be calculated based on an average of the probabilityincluded in the bottom sediment data calculated before 20 transmissionsstored in the bottom-sediment memory module 665, and the probabilityincluded in the bottom sediment data calculated by the bottom-sedimentdetermination module 52.

TABLE 2 Parameter Depth Rocks Sands Stones Mud Data 20 m 50(%) 50(%)0(%) 0(%)

Specifically, for example, as shown in Table 2 above, when theprobability of rocks is 50%, sands 50%, stones 0% and mud 0% in thebottom sediment data calculated before 20 transmissions, averages of theprobabilities shown in Table 1 and these probabilities may becalculated. As a result, the average of rocks may be 60%, sands 40%,stones 0% and mud 0%. Then, the texture count for each bottom sedimenttype may be calculated based on the average. Then, after sequentiallydisplaying 19 pieces of the rock textures from the corresponding displayposition, 13 pieces of the sand textures may be displayed so that a rateof the rock and sand textures may be approximately 60:40.

Further, the irregular display module 667 displays each type of texturesbased on the total count of the texture calculated by thetexture-total-count calculation module 664 and the count of the bottomsediment textures calculated by the bottom-sediment-texture-countcalculation module 666, downward from the bottom, as described above. Inthis embodiment, as similar to the irregular display module 663 inEmbodiment 1, the module 667 irregularly displays the textures so as tobe overlapped for each other in a range of 5-10 dots (approximately, ¼of a texture) in the vertical direction and ±5 dots in the horizontaldirection.

FIG. 8 shows a display example displayed as described above by theunderwater detection device 2. In FIG. 8, A1-A4 are the texturesdisplayed by the bottom-sediment display module 66′, and are in an orderof rocks, sands, stones and mud. B1 and B2 are the textures displayed bythe fish-type display module 63, and represent fish types in accordancewith the water depth. “C” represents a fish length (cm) of the fishdisplayed by the fish-length display module 62, and the fish texturewithout the indication of fish length can be considered as a shoal offish. “E” is a background displayed by the water-depth-variation displaymodule 64, to which darker gradation for deeper in water depth isapplied. Although FIG. 8 is indicated by gray scale for purpose, theunderwater detection device 2 may be capable of displaying by colorscale.

Further, a customization feature may also be added to the device so thatthe background can be changed based on the textures of bottom or fish,water depth and water temperature. Further, the textures and backgroundmay be imported from an external memory to enhance a variation thereof.Further, the textures and background may be changed by user'spreference. Further, the textures used for a bottom sediment type may betwo or more types.

1. An underwater detection device for detecting underwater bytransmission and reception of an ultrasonic signal, comprising: atransmission module for transmitting the ultrasonic signal underwater; areception module for receiving an echo signal of the transmittedultrasonic signal; a bottom detection module for detecting a bottombased on the echo signal from the bottom; a bottom-sedimentdetermination module for calculating probabilities of the bottomsediment on how much the bottom sediment contains each of predeterminedbottom sediment types based on the echo signal; and a bottom-sedimentdisplay module for displaying a texture representing each of the bottomsediment types below the bottom being displayed based on theprobabilities.
 2. The underwater detection device of claim 1, furthercomprising: a texture-total-count calculation module for calculating atotal count of the texture to be displayed below the bottom; and abottom-sediment-texture-count calculation module for calculating atexture count for each of the bottom sediment types based on the totalcount of the texture and the probabilities calculated by the bottomsediment determination module; wherein the bottom-sediment displaymodule displays based on the texture count for each of the bottomsediment types calculated by the bottom-sediment-texture-countcalculation module.
 3. The underwater detection device of claim 2,further comprising a bottom-sediment memory module for storing theprobabilities of the past calculated by the bottom-sedimentdetermination module, wherein the bottom-sediment-texture-countcalculation module calculates the texture count for each of the bottomsediment types based on the probabilities stored in the bottom-sedimentmemory module.
 4. The underwater detection device of claim 1, furthercomprising: a fish detection module for detecting a fish based on theecho signal received by the reception module; a fish-type determinationmodule for determining a type of the fish based on at least one of theecho signal, water temperature, water quality, water area and waterdepth; and a fish-type display module for displaying a texturerepresenting the fish type based on the fish type determined by thefish-type determination module.
 5. The underwater detection device ofclaim 1, further comprising a first water-depth-variation display modulefor varying the texture representing the bottom sediment or the fishdepending on a water depth.
 6. The underwater detection device of claim1, further comprising a second water-depth-variation display module fordisplaying a background to which gradation is applied based on a waterdepth.
 7. An underwater detection device for detecting underwater bytransmission and reception of an ultrasonic signal, comprising awater-depth-variation display module for displaying a background towhich gradation is applied based on a water depth.
 8. The underwaterdetection device of claim 7, wherein the water-depth-variation displaymodule applies the gradation only to a predetermined water depth range.9. The underwater detection device of claim 7, further comprising awater-temperature-variation display module for displaying a backgroundto which a color is applied based on a water temperature, wherein thegradation applied by the water-depth-variation display module is adarkness of the color of the background.
 10. An underwater detectionmethod for detecting underwater by transmission and reception of anultrasonic signal, comprising: transmitting the ultrasonic signalunderwater; receiving an echo signal of the transmitted ultrasonicsignal; detecting a bottom based on the echo signal from the bottom;calculating probabilities of the bottom sediment on how much the bottomsediment contains each of predetermined bottom sediment types based onthe echo signal; and displaying a texture representing each of thebottom sediment types below the bottom being displayed based on theprobabilities.
 11. The underwater detection method of claim 10, furthercomprising: calculating a total count of the texture to be displayedbelow the bottom; and calculating a texture count for each of the bottomsediment types based on the total count of the texture and thecalculated probabilities; wherein the texture is displayed based on thetexture count calculated for each of the bottom sediment types.
 12. Theunderwater detection method of claim 11, further comprising storing thecalculated probabilities of the past, wherein the texture count iscalculated for each of the bottom sediment types based on the storedprobabilities.
 13. The underwater detection method of claim 10, furthercomprising: detecting a fish based on the received echo signal;determining a type of the fish based on at least one of the echo signal,water temperature, water quality, water area and water depth; anddisplaying a texture representing the fish type based on the determinedfish type.
 14. The underwater detection method of claim 10, furthercomprising varying the texture representing the bottom sediment or thefish depending on a water depth.
 15. The underwater detection method ofclaim 10, further comprising displaying a background to which gradationis applied based on a water depth.
 16. An underwater detection methodfor detecting underwater by transmission and reception of an ultrasonicsignal, comprising displaying a background to which gradation is appliedbased on a water depth.
 17. The underwater detection method of claim 16,wherein the gradation is applied only to a predetermined water depthrange.
 18. The underwater detection method of claim 16, furthercomprising displaying a background to which a color is applied based ona water temperature, wherein the applied gradation is a darkness of thecolor of the background.